"Economy Dives as Goods Pile Up" from the February 1 issue of The Wall Street Journal goes over some finer details of 4th quarter performance.
In all quarters, some things get better and some get worse. In this one, the worst performers were business investment, consumer spending, and exports (basically, everyone else's business investment and consumer spending).
Interestingly, commercial and residential real estate were not off that much - perhaps they've fallen so far there isn't much place to go.
The only bright spot was imports - we're buying less of stuff produced by employees in other countries (although that is more than canceled by them not buying our stuff, and us not buying our stuff either).
The real problem area is inventories. These are goods that were produced but not sold. When they go up - as they did in the 4th quarter - it suggests that jobs will be cut more in the near future so that we don't make even more stuff that people aren't willing to buy.